Very recently (winter 2010), Unifying Hinduism: philosophy and identity in Indian intellectual history, a book by Andrew Nicholson raised interesting discussions on the “birth” of Hinduism. Nicholson locates it with interesting arguments in the Vijayanagara empire, but the results of any historical enterprise, may always be reframed within an earlier frame of references.
Jayanta Bhaṭṭa's attempt to admit the Atharvaveda among the Vedas and other Sacred Texts different than the Veda among the Texts enjoying an epistemological value (in the Āgamaprāmāṇya section of the Nyāyamañjarī) can be viewed as exactly part of the process which lead to the diffusion of a pan-Indian acceptance of similar texts and values.
Which enterprises would you classify as paving the way to "Hinduism"?
On Nicholson's book see also this post and this other blog (interview to Nicholson about his book, with comments). To Jayanta I dedicated many posts, see for instance here.